Single Drop Mass Transfer Research Articles

A state-of-the-art review on single drop study in liquid–liquid extraction: Experiments and simulations

Abstract The experimental and numerical investigations of single drop in liquid/liquid extraction system have been reviewed with particular focus on experimental techniques and computational fluid dynamic simulation approaches. Comprehensive surveys of available experimental techniques and numerical approaches for single drop rising and falling were given. Subsequently, single drop mass transfer was also reviewed both experimentally and numerically. Additionally, single drop breakage and coalescence process and the influencing factors were summarized and compared, so as to establish sub-models for population balance model. Future directions on single drop mass transfer, drop breakage and coalescence were suggested. It is believed that the single drop is a powerful tool to assist extraction process design from lab-scale to pilot-scale.

Effect of surfactant on single drop mass transfer for extraction of aromatics from lubricating oils

Solvent extraction is an effective method for the reduction of the content of aromatic of lubricating oil. Frequently, with phenol, furfural, the NMP (out of N-methyl pyrrolidone). The power solvent and the selectivity can be still to increase while using surfactant as additive which facilitates the separation of phase and increases the yeild in raffinat. Liquid-liquid mass transfer coefficients for single freely rising drops in the presence of surfactant in an extraction column have been investigated. The surfactant used in this study was sodium lauryl ether sulfate (SLES). The experiments were performed by bubbling a solvent as a series of individual drops from the top of the column containing furfural-SLES solution. The column used in this experiment was made from glass with 17 mm inner diameter and a capacity of 125ml. The effects of the concentration of surfactant on the overall coefficient of mass transfer was investigated.

Mass transfer enhancement at deformable droplets due to Marangoni convection

One of the key design parameters in liquid/liquid extraction is the mass transfer coefficient. A complex list of parameters including fluid dynamics, drop size distribution, chemical properties of the involved species, local interfacial instabilities (Marangoni convection) is required in order to determine the transient evolution of the mass transfer coefficient. The influence of Marangoni convection on single drop mass transfer cannot yet be described in an analytical manner, and empirical correlations available in literature fail to predict the mass transfer process. In the present study, experimental investigations on deformable single droplets in the toluene/acetone/water system are presented which shows strong interfacial instabilities. Parameters varied are the drop diameter, the initial solute concentration and the mass transfer direction. Experimental results are compared with the well-known models by Kronig and Brink and Handlos and Baron. The Kronig and Brink model cannot describe Marangoni dominated systems, but comparisons reveal the influence of deformation on the mass transfer enhancement. In contrary, with a slight modification to the Handlos and Baron model, the mean droplet concentration of the transferred component was successfully modelled as a function of Fourier number.

Effect of Surfactant on Single Drop Mass Transfer in Liquid-Liquid Extraction

Liquid-liquid mass transfer coefficients for single freely rising drops in the presence of surfactant in an extraction column have been investigated using the system of kerosene-acetic acid-water. The surfactant used in this study was alkyl benzene sulfonate (ABS). The experiments were carried out by bubbling kerosene-acetic acid solution as a series of single drops from the bottom of a column containing water-ABS solution. The column used in this experiment was made from glass of 36 mm inside diameter and constructed of 60, 120, and 180 cm height. The effects of surfactant concentration, column height, and drop diameter on the overall mass transfer coefficient have been studied. The data can all be correlated by Shd = 2.08 x10−5 Red 4.01 We −1.97 (dd / H ) 0.68 with an average deviation of 17.72%. This equation is valid for the ranges of Red from 186.68 to 402.19, We from 0.80 to 3.33, and dd/H from 0.0028 to 0.0105.

Simultaneous Effect of Contamination and Agitation on Mass Transfer of High Interfacial Tension Liquid–Liquid Extraction Systems

The influence of contamination and agitation on single drop mass transfer was investigated, using a pilot rotating disc contactor. The chemical system of toluene–acetone–water, having a high interfacial tension, was used with the advantage of high accuracy and repeatability in using GC for analysis. It is ideally required to account for the extent of contaimnation in a quantitative manner and in both phases with a single parameter. For this purpose and for design applications, an improvement was made on a combined mass transfer model, to be consistent with experimental data without mathematical assumption. The influence of drop size was also considered. Based on the series of experimental data, a correlation was proposed for the coefficient of this model.

Single drop mass transfer in ternary and quaternary liquid–liquid extraction systems

Single drop mass transfer data have been obtained for the ternary and quaternary systems toluene–acetone–water and toluene–acetone–phenol–water. The addition of surfactant was also made for some experiments. The results were assessed using a simple single solute mass transfer model and a non-equilibrium model based on the Maxwell–Stefan equations. In both cases allowance was made for the effects of interfacial contaminants or solutes by using empirical correlations for the mass transfer coefficients which were developed to take contamination into account. The non-equilibrium model rate-based calculations gave different results to the single solute model in the case that the two main solutes were undergoing simultaneous mass transfer. It is considered that the phenol is sufficiently interfacially-active to behave like a surfactant and this has major impact on mass transfer coefficients and hydrodynamic assumptions made for the non-equlibrium model. The concentrations of solute were relatively low and the non-equilibrium model did not indicate any notable degree of interaction of the mass transfer coefficients of the two main solutes. Chemical systems with much higher solute concentrations need to be investigated.

Single-drop mass transfer in the water-toluene-acetone system

An experimental study of fundamental mass-transfer characteristics was carried out in which acetone was transferred between water and toluene. All possible arrangements were involved; i.e., acetone was transferred in both directions, and both water and toluene were used as dispersed phases. With technical-grade solvents, the transfer rates were 2-10 times higher than calculated for rigid spheres, and on increasing the system purity, this increase grew to between 30 and 70 times. A previously derived empirical equation describes the low transfer rate results, while for the other case only rough estimations are possible due to the extreme sensitivity to small amounts of impurity

Single drop mass transfer augmented by interfacial instability

A photographic technique was used to determine mass transfer rates from single drops immediately following formation. Measurements were made on a system expected to exhibit interfacial tension driven convection and comparisons are drawn to predictions for stable systems and to measurements in the presence of surfactant. Unusually high mass transfer coefficients are reported.